A known charging device for secondary battery performs so-called additional charging by detecting a fully charged state of a secondary battery based on the temperature and voltage of the secondary battery, stopping charging when the fully charged state is detected and resuming charging after the elapse of a predetermined time after the stop. JP2003-143770A discloses a charging device for performing such additional charging, which device detects a peak voltage at the time of a full charge detection and increases a repeat count of additional charging as the peak voltage decreases.